The present invention relates to the field of power conversion systems, and more particularly to power supplies, inverters, and ballasts utilizing wire core inductive devices.
The overwhelming majority of electronic circuits require constant voltages to ensure appropriate operation. For example, many microcomputers require 5 volt and 12 volt sources capable of providing a current of 10 to 100 A. Other signal processing systems in which the currents produced vary with load conditions are required to maintain supply voltages at nearly constant levels (e.g., 5, 12, and 15 volts). In addition, many motor drives and control systems require dc supplies whose voltage levels are dynamically adjusted to meet desired operating conditions.
For portable systems, batteries may be used. More frequently, however, electronic circuits are energized by a circuit, or a power supply, which converts the alternating current waveform received from power lines (e.g., a 110 volt to 220 volt rms, 60-Hz sinusoid in the United States) to direct voltage of constant amplitude utilizing at least one transformer or inductive device. Often these systems power the device and charge the battery as well.
It is common and universal for low frequency application transformers and other inductive devices to be made up of a magnetic core comprising a plurality of sheets of steel, the sheets being die cut and stacked to create the desired thickness of a core. Individual sheets of selected thickness are oxide-coated, varnished or otherwise electrically insulated from one another in order to reduce/minimize eddy currents in the magnetic core. For many years the thickness (thus number of necessary pieces) of the stampings has been determined by a strict set of constraints-magnitude of eddy currents versus number of necessary pieces.
The magnetic core of a transformer or the like generally passes through the center of the electric winding, and closes on itself to provide a closed magnetic circuit. Since the magnetic core then supports the electric windings, it is natural that the core has also been used as the support for the transformer. That is to say, one attaches the magnetic core to a container or baseboard in order to support the transformer.
When a stack of metal sheets is used as the magnetic core for an inductive device, it is usual to provide a shape, such as an E with the electric windings on the center leg of the E. After the windings are in place, an additional stack of sheets usually in an I configuration is applied to connect the ends of the E, thereby completing the magnetic circuit. Using such a technique, it will be understood that the windings are necessarily wound separately, and subsequently placed on the magnetic core. The windings must therefore be large enough to slip onto the magnetic core.
Also, the shape of the windings is necessarily rectangular rather than circular which detracts from optimal operation. Such construction contributes to the inherent noisiness of an inductive device and necessarily the power conversion device, because the electric windings must be somewhat loose on the core. As a result, when an alternating voltage is applied to the electric windings, the sheets making up the core tend to vibrate with the alternating magnetic field or in sympathy in a subharmonic. Any resulting gaps and spaces between the electrical components and the magnetic components also reduce coupling and efficiency of action.
Transformers and other inductive devices inherently generate electromagnetic fields. Such fields external to the device lessen efficiency, as well as pose interferences to the immediately surrounding environment. Although the strength of these electromagnetic fields decreases with distance from the transformer, shielding of either the electromagnetic field source or the affected components is often required. As components in today""s electronics are made more sensitive and their packaging more dense, susceptibility to electromagnetic interaction increases dramatically. To assure optimum performance of these components, stray electromagnetic fields must be minimized often at a substantial cost. As noted above, one manner in which these fields may be minimized is to provide shielding around the source in order to contain the electromagnetic fields and to prevent interference from external sources.
Thus, a need exists for an improved power conversion system which may be manufactured in an efficient and cost effective manner and which utilizes transformers or other inductive devices which provide a high level of efficiency and superior shielding capabilities.
Accordingly, it is a primary object of the present invention to provide a novel and improved power conversion system and related method that are particularly adapted to be manufactured in an efficient and cost effective manner, and which overcome the limitations of the prior art.
Another object of the present invention is to provide a power conversion system that is particularly adapted to utilize an inductive device having a magnetic core formed from a plurality of wires.
Yet another object of the present invention is to provide a power conversion system which provides superior shielding capabilities.
Still another object of the present invention is to provide a power conversion system which houses all of its components within a magnetic core of an inductive device.
It is another object of the present invention to provide a method of making a power conversion system utilizing a plurality of wires to form a magnetic core.
Additional objects, advantages and other novel features of the invention will be set forth in part in the description that follows and in part will become apparent to those skilled in the art upon examination of the following or may be learned with the practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out in the appended claims.
To achieve the foregoing and other objects, and in accordance with the purposes of the present invention as described herein, there is provided an improved power conversion system which utilizes an inductive device having a magnetic core comprising a plurality of wires. The power conversion system can be any circuit that provides power with characteristics required by a load from an external power source with characteristics incompatible with the load, i.e., it makes the load compatible with the available external power source. Accordingly, the power conversion system may be any type of power supply, including but not limited to an analog power supply or a switch mode power supply, an inverter, a ballast, or the like.
An electric winding, or windings dependent upon the inductive device, is wound directly onto the plurality of wires forming the magnetic core. The ends of the wires forming the magnetic core are spread and formed over the electric windings, the two ends of the wires meeting to form a complete magnetic circuit. A band or other connector means holds the ends of the wires together. Advantageously, the wires formed in this manner envelop the electric windings and magnetic core to provide a shield substantially containing the electromagnetic fields emanating from the system and reducing the intrusion of electromagnetic fields from external sources. Additional shielding may be provided by binding at least a portion of the wires forming the shield with a transversely wound wire in place of the band.
In accordance with an important aspect of the present invention, the magnetic core of the inductive device may form a housing for some, or preferably all, of the remaining components of the power conversion system. For example, a typical analog power supply may include additional components such as a fuse, an on/off switch, a rectifier, a filter, and/or a regulator. In accordance with the present invention, these components would be housed within the housing formed by the magnetic core. In this manner, the inductive device, as well as the components of the power conversion system are physically protected and shielded against the intrusion of electromagnetic or radio frequency interferences from external sources. Further shielding can be accomplished by enclosing the interior of the transformer and the electronic components with shield plates.
The inductive device may include a mounting post bound within the plurality of wires forming the magnetic core and extending therefrom for supportably mounting the power conversion device. The mounting post may extend from either side or both sides of the magnetic core as desired. Also, the make-up of the magnetic core may be otherwise varied considerably. Wire of various diameters may be used to achieve greater density of the core; a few large wires may be spaced around the core to provide rigidity; and, one or more tubes may be incorporated into the core, the tubes carrying air or a fluid for cooling the inductive device and the power conversion device. The cooling tubes are preferably constructed of non-magnetic and non-electrical-conducting material.
In a further aspect of the invention, in accordance with its objects and purposes, a method of making a power conversion system includes the steps of forming the magnetic core of a plurality of wires, placing at least one electric winding along the length of the magnetic core, connecting the electric winding to the remaining components of the power conversion system, and shielding the inductive device by forming the wires of the magnetic core over the at least one electric winding to envelop the winding and form a complete magnetic circuit.
Still other objects of the present invention will become apparent to those skilled in this art from the following description wherein there is shown and described the preferred embodiments of this invention, simply by way of illustration of some of the modes best suited to carry out the invention. As it will be realized, the invention is capable of other different embodiments and its several details are capable of modification in various, obvious aspects all without departing from the invention. Accordingly, the drawings and descriptions will be regarded as illustrative in nature and not as restrictive.